This application relates to and incorporates herein by reference Japanese Patent Application No. 2002-133143 filed on May 8, 2002.
The present invention relates to an ignition control device for an internal combustion engine which rotates a crankshaft of the internal combustion engine having a cylinder in the forward direction and in the backward direction.
In a small-sized vehicle such as a scooter or a snow mobile, a reverse gear is not provided so as to reduce the size and lighten the weight. In this vehicle incapable of selecting the backward run by changing the gear, it is conceived to realize the backward run by reversing the rotating direction of the crankshaft of the internal combustion engine.
In an ignition system disclosed in JP-A-2001-152905, the crankshaft of an internal combustion engine can be rotated in the forward direction and in the backward direction at a low cost by using one sensor to reduce the number of parts and the number of assembling step. However, this ignition system is restricted by a condition, under which the center spacings, as taken in the rotating direction, of a pair of protrusions (or teeth) as the position detecting portions of a rotor rotating while facing the sensor, have to be substantially equal at three portions. Unless this restricting condition is satisfied, an erroneous determination tends to occur in the forward/backward rotating direction.
In case a similar ignition system is applied to an internal combustion engine having one cylinder (or a single cylinder), it is also desired for determining the forward/backward rotating direction quickly to arrange a pair of protrusions at three portions of the rotor. At the time of manufacturing the rotor, the degree of freedom of design is decreased in the positional relation of the protrusions.
It is therefore an object of the present invention to provide an ignition control device for an internal combustion engine, which can achieve a precise and stable ignition performance by a simple control in accordance with the running conditions even in either rotating direction, in case the center spacings of a pair of protrusions in the rotating direction are equal at least at two portions.
According to an ignition control device for an internal combustion engine, a pair of first position detecting portions and two pairs of second position detecting portions are formed on the outer circumference of a rotor, and only the length of one of the first position detecting portions is made different. The rotating direction of the crankshaft of the internal combustion engine having one cylinder is quickly determined on the basis of the detection result by one position detecting device with respect to one pair of first position detecting portions and two pairs of second position detecting portions, so that the ignition timing of the internal combustion engine is controlled precisely and stably according to the running condition.
Preferably, a rotation leading signal and a rotation trailing signal of the individual position detecting portions are produced on the basis of detection signals. Merely by comparing the previous signal production interval and present signal production interval on the base of those rotation leading signal and rotation trailing signal, it is found whether the rotating direction determination of the crankshaft of the internal combustion engine is proper. Therefore, the operation load on the rotating direction determination is reduced.
Preferably, the rotating direction of the internal combustion engine is determined, when the state, in which present signal production interval is longer than the last preceding signal production interval of the rotation leading signal or the rotation trailing signal, continues alternately but consecutively by predetermined number of times, on the basis of either the ratio of the signal production intervals of the rotation leading signals or the ratio of the signal production intervals of the rotation trailing signals.